A polyamide resin is excellent in a mechanical characteristic, a thermal property and a resistance to chemicals. Accordingly, it has been widely used as parts for automobiles, electric/electronic products, etc. In addition, a reinforced polyamide resin composition wherein polyamide is compounded with glass fiber exhibits a greatly improved mechanical characteristic, a greatly improved thermal property and a greatly improved resistance to chemicals. Therefore, investigations using the reinforced polyamide resin composition as a substitute material for metal have become brisk in view of a weight reduction, a rationalization of steps, etc.
Although a reinforced polyamide resin compounded with high concentrations of glass fiber, wollastonite, etc. can easily provide a molded product having a high rigidity, it is inferior in a weather resistance. Accordingly, an improvement is needed for using it outside. As to a method for improving the weather resistance, there have been proposals such as Patent Documents 1, 2 and 3.
In Patent Document 1, there is proposed a resin composition wherein poly-m-xylylene adipamide is compounded with an acrylic resin and an epoxy group-containing compound. In this resin composition, the epoxy group-containing compound is essential. Accordingly, a gel-like substance occurs or a melt fluidity lowers when a retention happens during a molding whereby an appearance of a molded product is deteriorated. In addition, a weather resistance is also insufficient. In Patent Document 2, there is proposed a resin composition comprising crystalline semi-aromatic polyamide as a main ingredient and further comprising glass fiber, wollastonite, carbon black and a copper compound. This resin composition has several deficiencies in terms of its production. Specifically, it is necessary to adopt a high molding resin temperature because the semi-aromatic polyamide is used as a main ingredient. In addition, a problem of abrasion of screw is unavoidable because wollastonite is compounded. When mica is compounded in place of wollastonite, it is impossible to sufficiently improve a weather resistance and to sufficiently prevent a fading in black color after exposure to a bad weather. Accordingly, there is yet a room for further improvements. In Patent Document 3, there is proposed a resin composition comprising a crystalline semi-aromatic polyamide as a main ingredient and further comprising glass fiber, wollastonite, specific carbon black and a copper compound. However, this resin composition has also the same deficiencies as those in Patent Document 2. In addition, it is necessary to use the specific carbon black. Further, when aliphatic polyamide is used as a main ingredient, it is impossible to sufficiently improve a weather resistance and to sufficiently prevent a fading in black color after exposure to a bad weather. Accordingly, there is yet a room for further improvements.